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Article 392 Cable Trays Part I. General 392.1 Scope. This article covers cable tray systems, including ladder, ventilated trough, ventilated channel, solid bottom, and other similar structures. Informational Note: See ANSI/NEMA–VE 1-2017, Metal Cable Tray Systems, and NECA/NEMA 105-2015, Standard...

Article 392 Cable Trays Part I. General 392.1 Scope. This article covers cable tray systems, including ladder, ventilated trough, ventilated channel, solid bottom, and other similar structures. Informational Note: See ANSI/NEMA–VE 1-2017, Metal Cable Tray Systems, and NECA/NEMA 105-2015, Standard for Installing Metal Cable Tray Systems, for further information on cable trays. ENHANCED CONTENT Collapse Cable trays are mechanical support systems and not raceways. See the definition of raceway in Article 100. Cable tray installations are typically an industrial-type wiring method. However, they are sometimes installed in commercial facilities as a wire-and-cable management system for telecommunications/data installations and for feeder and branch-circuit wiring. Pictured below is one example of Type MC cable installed in a wire mesh–type cable tray. (Courtesy of Legrand®) Part II. Installation 392.10 Uses Permitted. Cable tray shall be permitted to be used as a support system for wiring methods containing service conductors, feeders, branch circuits, communications circuits, control circuits, and signaling circuits. Single insulated cables and single insulated conductors shall be permitted in cable tray only when installed in accordance with 392.10(B)(1). Cable tray installations shall not be limited to industrial establishments. Where exposed to direct rays of the sun, insulated conductors and jacketed cables shall be identified as being sunlight resistant. Cable trays and their associated fittings shall be identified for the intended use. Wiring Methods. The wiring methods in Table 392.10(A) shall be permitted to be installed in cable tray systems under the conditions described in their respective articles and sections. Table 392.10(A) Wiring Methods Wiring Method Article Armored cable: Type AC 320 CATV cables 800 and 820 Class 2 and Class 3 cables 722 and 725 Communications cables 800 and 805 Communications raceways 800 Electrical metallic tubing: EMT 358 Electrical nonmetallic tubing: ENT 362 Fire alarm cables 722 and 760 Flexible metal conduit: FMC 348 Flexible metallic tubing: FMT 360 Instrumentation tray cable: Type ITC 341 Intermediate metal conduit: IMC 342 Liquidtight flexible metal conduit: LFMC 350 Liquidtight flexible nonmetallic conduit: LFNC 356 Metal-clad cable: Type MC 330 Mineral-insulated, metal-sheathed cable: Type MI 332 Network-powered broadband communications cables 800 and 830 Nonmetallic-sheathed cable: Types NM, NMC, and NMS 334 Non–power-limited fire alarm cable 722 and 760 Optical fiber cables 722 and 770 Other factory-assembled, multiconductor control, signal, or power cables that are specifically approved for installation in cable trays Power and control tray cable: Type TC 336 Power-limited fire alarm cable 722 and 760 Power-limited tray cable 725 Rigid metal conduit: RMC 344 Rigid polyvinyl chloride conduit: PVC 352 Reinforced thermosetting resin conduit: RTRC 355 Service-entrance cable: Types SE and USE 338 Underground feeder and branch-circuit cable: Type UF 340 ENHANCED CONTENT Collapse Metal cable trays can be used in other spaces used for environmental air (plenums) to support recognized wiring methods permitted in those spaces. Metal cable trays are not the limiting factor; rather, the cable or wiring method is. In Industrial Establishments. The wiring methods in Table 392.10(A) shall be permitted to be used in any industrial establishment under the conditions described in their respective articles. In industrial establishments only, where conditions of maintenance and supervision ensure that only qualified persons service the installed cable tray system, any of the cables in 392.10(B)(1) and (B)(2) shall be permitted to be installed in ladder, ventilated trough, solid bottom, or ventilated channel cable trays. Single-Conductor Cables and Single Insulated Conductors. Single-conductor cables and single insulated conductors shall be permitted to be installed in accordance with 392.10(B)(1)(a) through (B)(1)(c). Single-conductor cables and single insulated conductors shall be 1/0 AWG or larger and shall be of a type listed and marked on the surface for use in cable trays. Where 1/0 AWG through 4/0 AWG single-conductor cables and single insulated conductors are installed in ladder cable tray, the maximum allowable rung spacing for the ladder cable tray shall be 225 mm (9 in.). Welding cables shall comply with Article 630, Part IV. Single conductors used as equipment grounding conductors shall be insulated, covered, or bare, and they shall be 4 AWG or larger. ENHANCED CONTENT Collapse See also 630.42, which requires that trays used to support welding cables be dedicated for welding cable installation. Single- and Multiconductor Medium Voltage Cables. Single- and multiconductor medium voltage cables shall be Type MV cable. Single conductors shall be installed in accordance with 392.10(B)(1). Hazardous (Classified) Locations. Cable trays in hazardous (classified) locations shall contain only the cable types and raceways permitted by other articles in this Code. Nonmetallic Cable Tray. In addition to the uses permitted elsewhere in 392.10, nonmetallic cable tray shall be permitted in corrosive areas and in areas requiring voltage isolation. ENHANCED CONTENT Collapse Fiberglass cable trays are often used to support cables in corrosive environments or in electrolytic cell rooms where voltage isolation is required. Airfield Lighting Cable Tray. In airports where maintenance and supervision conditions ensure that only qualified persons can access, install, or service the cable, airfield lighting cable used in series circuits that are rated up to 5000 volts and are powered by constant current regulators shall be permitted to be installed in cable trays. Informational Note: Federal Aviation Administration (FAA) Advisory Circulars (ACs) provide additional practices and methods for airport lighting. ENHANCED CONTENT Collapse See also FAA AC 150/5345-7F, Specification for L-824 Underground Electrical Cable for Airport Lighting Circuits; FAA AC 150/5345-42J, Specification for Airport Light Bases, Transformer Housings, Junction Boxes, and Accessories; and FAA AC 150/5345-26E, FAA Specification for L-823 Plug and Receptacle, Cable Connectors, which are available for free download from www.faa.gov. 392.12 Uses Not Permitted. Cable tray systems shall not be used in hoistways or where subject to severe physical damage. 392.18 Cable Tray Installation. (A) Complete System. Cable trays shall be installed as a complete system. Field bends or modifications shall be so made that the electrical continuity of the cable tray system and support for the cables is maintained. Cable tray systems shall be permitted to have mechanically discontinuous segments between cable tray runs or between cable tray runs and equipment. ENHANCED CONTENT Collapse Runs of cable tray are not required to be mechanically continuous from the equipment source to the equipment termination. Breaks in the mechanical continuity of cable tray systems are permitted and often occur at tees, crossovers, elevation changes, or firestops, or for thermal contraction and expansion. Also, cable tray systems are not required to be mechanically connected to the equipment they serve. Completed Before Installation. Each run of cable tray shall be completed before the installation of cables. Covers. In portions of runs where additional protection is required, covers or enclosures providing the required protection shall be of a material that is compatible with the cable tray. Through Partitions and Walls. Cable trays shall be permitted to extend transversely through partitions and walls or vertically through platforms and floors in wet or dry locations where the installations, complete with installed cables, are made in accordance with 300.21. Exposed and Accessible. Cable trays shall be exposed and accessible, except as permitted by 392.18(D). Adequate Access. Sufficient space shall be provided and maintained about cable trays to permit adequate access for installing and maintaining the cables. Raceways, Cables, Boxes, and Conduit Bodies Supported from Cable Tray Systems. In industrial facilities where conditions of maintenance and supervision ensure that only qualified persons service the installation and where the cable tray systems are designed and installed to support the load, such systems shall be permitted to support raceways and cables, and boxes and conduit bodies covered in 314.1. For raceways terminating at the tray, a listed cable tray clamp or adapter shall be used to securely fasten the raceway to the cable tray system. Additional supporting and securing of the raceway shall be in accordance with the appropriate raceway article. For raceways or cables running parallel to and attached to the bottom or side of a cable tray system, fastening and supporting shall be in accordance with the appropriate raceway or cable article. For boxes and conduit bodies attached to the bottom or side of a cable tray system, fastening and supporting shall be in accordance with 314.23. ENHANCED CONTENT Collapse Conduit and cable termination supports as well as outlet boxes are permitted to be supported solely by the cable tray in qualifying industrial facilities only. These items are not permitted to be supported solely by the cable tray in commercial installations. For commercial installations (and nonqualifying industrial facilities), conduit must be supported within 3 feet of the cable tray, or within 5 feet if structural members do not permit fastening within 3 feet of the cable tray. Cables connecting to equipment outside the cable tray system must be supported according to their respective NEC articles. Marking. Cable trays containing conductors operating over 600 volts shall have a permanent, legible warning notice carrying the wording “DANGER — HIGH VOLTAGE — KEEP AWAY” placed in a readily visible position on all cable trays, with the spacing of warning notices not to exceed 3 m (10 ft). The danger marking(s) or labels shall comply with 110.21(B). Exception: Where not accessible (as applied to equipment), in industrial establishments where the conditions of maintenance and supervision ensure that only qualified persons service the installation, cable tray system warning notices shall be located where necessary for the installation to ensure safe maintenance and operation. 392.20 Cable and Conductor Installation. (A) Multiconductor Cables Operating at 1000 Volts or Less. Multiconductor cables operating at 1000 volts or less shall be permitted to be installed in the same tray. Cables Operating at Over 1000 Volts. Cables operating at over 1000 volts and those operating at 1000 volts or less instal⁠led in the same cable tray shall comply with either of the following: The cables operating at over 1000 volts are Type MC. The cables operating at over 1000 volts are separated from the cables operating at 1000 volts or less by a solid fixed barrier of a material compatible with the cable tray. Connected in Parallel. Where single conductor cables comprising each phase, neutral, or grounded conductor of an alternating-current circuit are connected in parallel as permitted in 310.10(G), the conductors shall be installed in groups consisting of not more than one conductor per phase, neutral, or grounded conductor to prevent current imbalance in the paralleled conductors due to inductive reactance. Single conductors shall be securely bound in circuit groups to prevent excessive movement due to fault-current magnetic forces unless single conductors are cabled together, such as triplexed assemblies. Single Conductors. Where any of the single conductors installed in ladder or ventilated trough cable trays are 1/0 through 4/0 AWG, all single conductors shall be installed in a single layer. Conductors that are bound together to comprise each circuit group shall be permitted to be installed in other than a single layer. 392.22 Number of Conductors or Cables. (A) Number of Multiconductor Cables, Rated 2000 Volts or Less, in Cable Trays. The number of multiconductor cables, rated 2000 volts or less, permitted in a single cable tray shall not exceed the requirements of this section. The conductor sizes shall apply to both aluminum and copper conductors. Where dividers are used, fill calculations shall apply to each divided section of the cable tray. Ladder or Ventilated Trough Cable Trays Containing Any Mixture of Cables. Where ladder or ventilated trough cable trays contain multiconductor power or lighting cables, or any mixture of multiconductor power, lighting, control, and signal cables, the maximum number of cables shall conform to 392.22(A)(1)(a) through (A)(1)(c). Where all of the cables are 4/0 AWG or larger, the sum of the diameters of all cables shall not exceed the cable tray width, and the cables shall be installed in a single layer. Where the cable ampacity is determined according to 392.80(A)(1)(c), the cable tray width shall not be less than the sum of the diameters of the cables and the sum of the required spacing widths between the cables. Where all of the cables are smaller than 4/0 AWG, the sum of the cross-sectional areas of all cables shall not exceed the maximum allowable cable fill area in Column 1 of Table 392.22(A)(1) for the appropriate cable tray width. Where 4/0 AWG or larger cables are installed in the same cable tray with cables smaller than 4/0 AWG, the sum of the cross-sectional areas of all cables smaller than 4/0 AWG shall not exceed the maximum allowable fill area resulting from the calculation in Column 2 of Table 392.22(A)(1) for the appropriate cable tray width. The 4/0 AWG and larger cables shall be installed in a single layer, and no other cables shall be placed on them. Table 392.22(A)(1) Allowable Cable Fill Area for Multiconductor Cables in Ladder, Ventilated Trough, or Solid Bottom Cable Trays for Cables Rated 2000 Volts or Less Inside Width of Cable Tray Maximum Allowable Fill Area for Multiconductor Cables Ladder or Ventilated Trough or Wire Mesh Cable Trays, 392.22(A)(1) Solid Bottom Cable Trays, 392.22(A)(3) Column 1 Applicable for 392.22(A)(1)(b) Only Column 2a Applicable for 392.22(A)(1)(c) Only Column 3 Applicable for 392.22(A)(3)(b) Only Column 4a Applicable for 392.22(A)(3)(c) Only mm in. mm2 in.2 mm2 in.2 mm2 in.2 mm2 in.2 50 2.0 1,500 2.5 1,500 – (30 Sd)b 2.5 – (1.2 Sd)b 1,200 2.0 1,200 – (25 Sd)b 2.0 – Sdb 100 4.0 3,000 4.5 3,000 – (30 Sd)b 4.5 – (1.2 Sd) 2,300 3.5 2,300 – (25 Sd) 3.5 – Sd 150 6.0 4,500 7.0 4,500 – (30 Sd)b 7 – (1.2 Sd) 3,500 5.5 3,500 – (25 Sd)b 5.5–Sd 200 8.0 6,000 9.5 6,000 – (30 Sd)b 9.5 – (1.2 Sd) 4,500 7.0 4,500 – (25 Sd) 7.0 – Sd 225 9.0 6,800 10.5 6,800 – (30 Sd) 10.5 – (1.2 Sd) 5,100 8.0 5,100 – (25 Sd) 8.0 – Sd 300 12.0 9,000 14.0 9,000 – (30 Sd) 14 – (1.2 Sd) 7,100 11.0 7,100 – (25 Sd) 11.0 – Sd 400 16.0 12,000 18.5 12,000 – (30 Sd) 18.5 – (1.2 Sd) 9,400 14.5 9,400 – (25 Sd) 14.5 – Sd 450 18.0 13,500 21.0 13,500 – (30 Sd) 21 – (1.2 Sd) 10,600 16.5 10,600 – (25 Sd) 16.5 – Sd 500 20.0 15,000 23.5 15,000 – (30 Sd) 23.5 – (1.2 Sd) 11,800 18.5 11,800 – (25 Sd) 18.5 – Sd 600 24.0 18,000 28.0 18,000 – (30 Sd) 28 – (1.2 Sd) 14,200 22.0 14,200 – (25 Sd) 22.0 – Sd 750 30.0 22,500 35.0 22,500 – (30 Sd) 35 – (1.2 Sd) 17,700 27.5 17,700 – (25 Sd) 27.5 – Sd 900 36.0 27,000 42.0 27,000 – (30 Sd) 42 – (1.2 Sd) 21,300 33.0 21,300 – (25 Sd) 33.0 – Sd aThe maximum allowable fill areas in Columns 2 and 4 shall be calculated. For example, the maximum allowable fill in mm2 for a 150-mm wide cable tray in Column 2 shall be 4500 minus (30 multiplied by Sd) [the maximum allowable fill, in square inches, for a 6-in. wide cable tray in Column 2 shall be 7 minus (1.2 multiplied by Sd)]. bThe term Sd in Columns 2 and 4 is equal to the sum of the diameters, in mm, of all cables 107.2 mm (in inches, of all 4/0 AWG) and larger multiconductor cables in the same cable tray with smaller cables. Ladder or Ventilated Trough Cable Trays Containing Multiconductor Control and/or Signal Cables Only. Where a ladder or ventilated trough cable tray having a usable inside depth of 150 mm (6 in.) or less contains multiconductor control and/or signal cables only, the sum of the cross-sectional areas of all cables at any cross section shall not exceed 50 percent of the interior cross-sectional area of the cable tray. A depth of 150 mm (6 in.) shall be used to calculate the allowable interior cross-sectional area of any cable tray that has a usable inside depth of more than 150 mm (6 in.). Solid Bottom Cable Trays Containing Any Mixture of Cables. Where solid bottom cable trays contain multiconductor power or lighting cables, or any mixture of multiconductor power, lighting, control, and signal cables, the maximum number of cables shall conform to 392.22(A)(3)(a) through (A)(3)(c). Where all of the cables are 4/0 AWG or larger, the sum of the diameters of all cables shall not exceed 90 percent of the cable tray width, and the cables shall be installed in a single layer. Where all of the cables are smaller than 4/0 AWG, the sum of the cross-sectional areas of all cables shall not exceed the maximum allowable cable fill area in Column 3 of Table 392.22(A)(1) for the appropriate cable tray width. Where 4/0 AWG or larger cables are installed in the same cable tray with cables smaller than 4/0 AWG, the sum of the cross-sectional areas of all cables smaller than 4/0 AWG shall not exceed the maximum allowable fill area resulting from the computation in Column 4 of Table 392.22(A)(1) for the appropriate cable tray width. The 4/0 AWG and larger cables shall be installed in a single layer, and no other cables shall be placed on them. Solid Bottom Cable Tray Containing Multiconductor Control and/or Signal Cables Only. Where a solid bottom cable tray having a usable inside depth of 150 mm (6 in.) or less contains multiconductor control and/or signal cables only, the sum of the cross sectional areas of all cables at any cross section shall not exceed 40 percent of the interior cross-sectional area of the cable tray. A depth of 150 mm (6 in.) shall be used to calculate the allowable interior cross-sectional area of any cable tray that has a usable inside depth of more than 150 mm (6 in.). Ventilated Channel Cable Trays Containing Multiconductor Cables of Any Type. Where ventilated channel cable trays contain multiconductor cables of any type, 392.22(A)(5)(a) and (A)(5)(b) shall apply. Where only one multiconductor cable is installed, the cross-sectional area shall not exceed the value specified in Column 1 of Table 392.22(A)(5). Where more than one multiconductor cable is instal⁠led, the sum of the cross-sectional area of all cables shall not exceed the value specified in Column 2 of Table 392.22(A)(5). Table 392.22(A)(5) Allowable Cable Fill Area for Multiconductor Cables in Ventilated Channel Cable Trays for Cables Rated 2000 Volts or Less Inside Width of Cable Tray Maximum Allowable Fill Area for Multiconductor Cables Column 1 One Cable Column 2 More Than One Cable mm in. mm2 in.2 mm2 in.2 75 3 1500 2.3 850 1.3 100 4 2900 4.5 1600 2.5 150 6 4500 7.0 2450 3.8 Solid Channel Cable Trays Containing Multiconductor Cables of Any Type. Where solid channel cable trays contain multiconductor cables of any type, 392.22(A)(6)(a) and (A)(6)(b) shall apply. Where only one multiconductor cable is installed, the cross-sectional area of the cable shall not exceed the value specified in Column 1 of Table